Nanoengineered Coating Uses Naturally Occurring
Water Deep in Earth to Power Underground Oil and Gas
Sensors

Rensselaer Polytechnic Institute Professor Nikhil Koratkar is
leading a $1 million study to develop new coatings for
nanosensors that could lead to more accurate and efficient oil
exploration.

Koratkar and colleagues are investigating how the flow of
water, steam, or certain gasses over surfaces coated with
carbon nanotubes or graphene can generate small amounts of
electricity. The researchers seek to explain this phenomenon —
which has been observed but is not yet fully understood — and
use their findings to create tiny self-powered devices that
travel through naturally occurring cracks deep in the earth and
can help uncover hidden pockets of oil and natural gas.

“Water and gases are naturally moving deep within crevices
in the earth, so we are investigating the best way to harvest
that energy and put it to use,” said Koratkar, professor in the
Department of Mechanical,
Aerospace, and Nuclear Engineering in Rensselaer’s School of Engineering.
“It has been shown that the flow of water and gases over
certain nanomaterials creates an electric charge, but we’re
still not quite sure why. Once we fully understand the reason,
we should be able to optimize the process and create a
practical, useful device.”

The three-year study, funded by the Advanced Energy
Consortium, is titled “Nanofluidic Power Generation Using
One-Dimensional (Carbon Nanotube) and Two-Dimensional
(Graphene) Nanomaterials.”

Hydrocarbon exploration is an expensive process that
involves drilling deep down in the earth to detect the presence
of oil or natural gas. Koratkar said oil and gas companies
would like to augment this process by sending out large numbers
of nanoscale sensors into new and existing drill wells. These
sensors would travel laterally through the earth, carried by
the naturally occurring water and gas flowing through the
network of cracks that exists underneath the earth’s surface.
Oil companies would no longer be limited to vertical
exploration, and the data collected from the sensors would arm
these firms with more information for deciding the best
locations to drill.

A key challenge to realizing these nanosensors, Koratkar
said, is that they are autonomous and therefore need to be
self-powered. Recent studies show that the motion of water over
carbon nanotubes creates small amounts of electricity—but far
less than needed to power the sensors. Koratkar’s team is
investigating how to optimize this process and exploit it to
generate electricity on the order of milliwatts. In addition to
coating a nanosensor with carbon nanotubes, the team will also
look at using coatings made from graphene, a single-atom-thick
sheet of carbon atoms arranged like a nanoscale chain-link
fence.

Conventional thinking is that free electrons on the surface
of carbon nanotubes and graphene can interact with ions in the
flowing water. The ions can drag the electrons in the flow
direction, creating an electric current. It is curious,
Koratkar said, that flowing steam over carbon nanotubes creates
a voltage, even though steam does not contain ions—a mystery
the new study plans to tackle. Additionally, his team will
investigate how water flowing inside of carbon nanotubes, and
inside of layered graphene, can be harnessed to create
additional voltage.

“We don’t fully understand everything about this process,
but once we do, it should lead to exciting new possibilities
for nanocoatings that can power sensors by harvesting energy
from their environment,” Koratkar said. “This should help the
drilling companies locate and identify new pockets of oil and
natural gas that have so far gone unnoticed.”